This application claims the benefit of International Application Number PCT/CH99/00430, which was published in English on Apr. 13, 2000.
The invention relates to a bellows-type cover made from elastic material, such as rubber or plastic material, used, for instance, for the protection of universal joints and drive shafts in which a clamping member or members such as hose clamps or shrinkable compression rings are integrated with the bellows-type cover.
Flexible or elastic bellows-type covers usually of accordion-like construction, such as axle boots for universal joints or for drive shafts, must be carefully sealed to protect the lubricant. Such bellows-type covers have been used extensively in the automotive industry, for example to protect joints at a drive shaft. They are normally fastened to the axle stub shafts by means of hose clamps or shrinkable compression rings. A need exists at present on the part of manufacturers of universal joint shafts or drive shafts for bellows-type covers in which clamping members in the form of xe2x80x9cOetikerxe2x80x9d hose clamps or xe2x80x9cOetikerxe2x80x9d shrinkable compression rings are already integrated into the bellows-type covers. In other words, the manufacturers desire a product in which the clamping members are already integrated at or in the bellows-type covers which favours the automatic assembly of the universal joint or drive shafts in that the bellows-type covers provided with integrated clamping members are available as pre-assembled parts so as to avoid the need for mounting the clamping members on the bellows-type covers only at the final assembly as is often the case today.
Two possibilities exist, in principle, for a clamping member to be integrated into the bellows-type cover which consist of (1) the clamping member vulcanised into the bellows-type cover or (2) a self-holding arrangement for a clamping member adapted to be mounted on the bellows-type cover. Of these two possibilities, the first solution involving the clamping member vulcanised into the bellows-type cover can be disregarded because such an arrangement is practically not feasible with the usual hose clamps presently used as clamping members as also with compression rings used as clamping members. For example, a stepless hose clamp of the type disclosed in the U.S. Pat. No. 4,299,012, which has been used extensively with axle boots in the automotive industry, if vulcanised into the bellows-type cover, would present great difficulty of being tightened by deforming the xe2x80x9cOetikerxe2x80x9d ear. The vulcanised-in solution is also unacceptable because of substantial increase in costs. A shrinkable compression ring, vulcanised into the bellows-type cover can no longer be shrunk by means of the presently available tools because these tools are designed to engage during the shrinking operation with the external surface of the compression ring having a predetermined diameter in a form-locking manner in order to reduce the compression ring in its diametric dimension by the application of radial forces. The layer of rubber or plastic material applied over the vulcanised-in shrinkable compression ring formed by the vulcanising operation prevents a form-locking connection between the compression ring and the compression tool. Equally inappropriate are arguments that vulcanising-in of the clamping members into the bellows-type covers provides a corrosion protection of the integrated hose clamps or compression rings because these problems can be readily avoided in the present invention by the use of approximate materials for the clamping devices, such as stainless steel or aluminum. Furthermore, a vulcanising-in of the clamping members precludes any visual control provided at the clamping member in the installed condition insofar as correct positioning and seating of the clamping member and proper tightening of the clamping member are concerned. Visual inspection of indications relating to manufacturer of the clamping members and/or installation dates would also become impossible. Up to the present, hose clamps used with drive or universal joint shafts have served extensively as information carriers in that dates such as assembly dates or other relevant dates of interest to the manufacturer were integrated into the clamping devices, for example, by stamping. Such visual inspections and controls are possible only as long as the clamping members are freely exposed which is not the case with a vulcanised-in solution.
Therefore, as a consequence the EP 0 809 034 proposes a bellows-type cover with integrated clamping member, which is adapted to be securely integrated to form a preassembled unit. A groove-shaped recess near one end of the bellows-type cover adapted to receive the clamping member has a two-tier positioning arrangement with a radially inward, circumferentially extending bottom surface for engagement by the clamping member when fully tightened and with a temporary bottom for the clamping member to provide a releasable self-retaining support for the closed, but not yet fully tightened clamping member at a radial distance between the bottom surface and the radially outer limit of the recess. Due to new production techniques for such kind of bellows-type cover members, such as blow injection or blow extrusion, it became very difficult or even impossible to produce the proposed bellows-type covers with integrated clamping members according to the EP 0 809 034.
Therefore, it is an object of the present invention to provide a bellows-type cover member with an integrated clamping member, similar to the one proposed in the EP 0 809 034 with the difference, that the bellows-type cover can easily be produced using new plastics processing techniques.
According to one embodiment of this invention, the pre-assembled unit consists of a bellows-type cover of rubber or plastic material and of an xe2x80x9cOetikerxe2x80x9d shrinkable compression ring or hose clamp of metal, both readily mass-producible items, in which the clamping member, as customary to date, is installed between first and second retaining means protruding from the external diameter for receiving the clamping member at both ends of the bellows-type cover, i.e., in the small as also in the large outer diameter area of the bellows-type cover. To date, often groove-shaped recesses formed by fully around extending retaining means serve exclusively for the correct guidance of the clamping member in the fully installed condition but are unable to provide any self-retaining function for a pre-assembled clamping member such as a compression ring integrated into the bellows-type cover.
As mentioned above in that respect the EP 0 809 034 proposes circumferentially extending bottom surfaces, which are an integral part of the around extending retaining means. In principle this circumferentially extending bottom surface, which provides a releasable self-retaining support, makes it possible to arrange a clamping member to form a preassembled unit to overcome the disadvantages of the still often used bellows-type cover members as mentioned above. The disadvantage of the arrangement according to the EP 0 809 034 is that it is practically impossible to produce the bellows-type cover using modern plastics processing techniques, such as blow moulding or blow extrusion. The difference of the inventive embodiment is that a further means is proposed to provide a self-retaining support for the clamping member in a preassembled position at a distance of the bottom surface of the bellows-type cover member between the first and the second retaining means, which is not an integral part of the mentioned first and second retaining means, but which is arranged at a distance from the first retaining means as well as from the second retaining means.
According to a preferred embodiment of this invention, the bellows-type cover at the section of the retaining means for receiving the clamping member is of two-tier construction in that it is now provided with at least one, preferably with several, detent elements along the circumference thereof between the retaining means which position and hold the compression ring in a self-retaining manner, once placed between the retaining means prior to tightening or shrinking of the clamping member. The clamping member, such as a compression ring, can now be removed again from the bellows-type cover only with the use of large forces. As a result thereof, the clamping member such as a compression ring which is now automatically retained after being mounted on the bellows-type cover between the retaining means, now forms an integrated unit with the bellows-type cover for further processing the integrated unit of bellows-type cover and clamping member. The use of detent elements offers the advantage of providing a two-tier structure for accommodating the clamping member in which the radially outer position securely but only temporarily holds the clamping member as a part integrated into the bellows-type cover yet permits complete, reliable tightening of the clamping member by releasing the temporary radially outer position in the presence of predetermined tightening forces. The term xe2x80x9cclamping memberxe2x80x9d is used in this application to describe both conventional clamps such as xe2x80x9cOetikerxe2x80x9d stepless clamps as presently used with bellows-type covers as also shrinkable compression rings such as xe2x80x9cOetikerxe2x80x9d. puzzle lock compression rings as disclosed in U.S. Pat. Nos. 5,001,816 and 5,185,908, or any other kind of so-called press rings, clamping rings or shrinkable compression rings.